Vaccinia NPH-I, a DExH-box ATPase, is the energy coupling factor for mRNA transcription termination.
Vaccinia virus RNA polymerase terminates transcription in response to a specific signal UUUUUNU in the nascent RNA. Transduction of this signal to the elongating polymerase requires a trans-acting viral termination factor (VTF/capping enzyme), and is coupled to the hydrolysis of ATP. Recent studies suggest that ATP hydrolysis is catalyzed by a novel termination protein (factor X), which is tightly associated with the elongation complex. Here, we identify factor X as NPH-I (nucleoside triphosphate phosphohydrolase-I), a virus-encoded DNA-dependent ATPase of the DExH-box family. We report that NPH-I serves two roles in transcription (1) it acts in concert with VTF/CE to catalyze release of UUUUUNU-containing nascent RNA from the elongation complex, and (2) it acts by itself as a polymerase elongation factor to facilitate readthrough of intrinsic pause sites. A mutation (K61A) in the GxGKT motif of NPH-I abolishes ATP hydrolysis and eliminates the termination and elongation factor activities. Related DExH proteins may have similar roles at postinitiation steps during cellular mRNA synthesis.
Deng
L
L
Molecular Biology Program, Sloan-Kettering Institute, New York, New York 10021, USA.
Shuman
S
S
D017766:Acid Anhydride Hydrolases / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D004734:Energy Metabolism; D006493:Heparin / Q000494:pharmacology; D008957:Models, Genetic; D008969:Molecular Sequence Data; D043583:Nucleoside-Triphosphatase; D012333:RNA, Messenger / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D013728:Terminator Regions, Genetic; D014158:Transcription, Genetic / Q000187:drug effects; D014616:Vaccinia virus / Q000201:enzymology* / Q000235:genetics; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
D012333:RNA, Messenger; D011994:Recombinant Proteins; D014764:Viral Proteins; D006493:Heparin; D017766:Acid Anhydride Hydrolases; D000251:Adenosine Triphosphatases; D043583:Nucleoside-Triphosphatase